As a sensor for detecting a rotation speed and a rotation angle of a rotating member, various types of detecting apparatuses have been used. Japanese Patent Laid-Open Publication No. Hei 7-306218, for example, discloses that a rotation speed of a wheel is detected using a wheel speed sensor of an electromagnetic pickup type. On the other hand, Japanese Patent Laid-Open Publication No. 2004-77136 discloses detection of a rotation angle of a motor using a resolver.
Further, a method of detecting a rotation speed of a motor is disclosed in Japanese Patent Laid-Open Publications No. 2002-112580 and No. Sho 63-220788.
When a rotation speed of a rotating member is detected using an output signal from a sensor, a signal which has been output in a past time period prior to a detection time is used, taking into account the possibility that noise may be mixed into the output signal from the sensor. Accordingly, the rotation speed detected using the output signal from the sensor has a response delay relative to an actual rotation speed at the detection time. Further, when rotation speeds of a plurality of rotating members are detected using output signals from a plurality of sensors having different characteristics, the detected rotation speeds of the rotating members differ in length of response delay times due to different characteristics of the sensors. On the other hand, when a rotation speed of each rotating member is detected using a time length of pulse intervals in a predetermined number of pulse signals output from, for example, an electromagnetic pickup sensor, the length of response delay time in the detected rotation speed of each rotating member will change in accordance with an actual rotation speed (the time length of pulse intervals).
As such, when rotation speeds of a plurality of rotating members are detected using output signals from separate sensors, the length of response delay time occurring in the detected rotation speeds might vary for each of the sensors. Such a difference in the length of response delay time results in a problem that accuracy of detecting the rotation speed varies for each rotating member. Further, when speed change control of an automatic transmission is performed, for example, it is necessary for rotation speeds of an input shaft and an output shaft to be separately detected using output signals from different sensors. In the detection, if the accuracy of detecting the rotation speed is inconsistent between the input shaft and the output shaft, accuracy of the speed change control is in turn lowered, thereby causing gear shift shock to occur during switching of a frictional engagement device to be engaged.
The present invention advantageously provides a rotation speed detecting apparatus capable of detecting rotation speeds of a plurality of rotating members using output signals from different sensors, while maintaining consistent accuracy in the detection of rotation speeds of the rotating members. Further, the present invention provides an automatic transmission controller in which accuracy of speed change control can be improved.